SYCAMORE – William "Billy" Curl's bid to have a judge toss his 37-year prison sentence for murdering Northern Illinois University student Antinette “Toni” Keller might come down to math.

Curl, 36, formerly of DeKalb, had 30 days from the time he entered the negotiated plea agreement April 3 to file a motion trying to undo it, prosecutors said. He didn't file the motion until July 22, which is 108 days after he entered the plea.

Curl appeared in DeKalb County Circuit Court on Tuesday for the first time since filing the request, which claims prosecutors threatened his 13-year-old son. He also has claimed his dyslexia, speech impediment and “great difficulty” reading and writing prevented him from understanding the finality of the agreement.